Moore's law describes a long-term trend in the history of computing hardware, in which the number of transistors that can be placed inexpensively on an integrated circuit has doubled approximately every two years. The capabilities of many digital electronic devices are strongly linked to Moore's law: processing speed, memory capacity, sensors and even the number and size of pixels in digital cameras. All of these are improving at (roughly) exponential rates as well. Currently, the design node is shrinking to 22 nm or even smaller, however, this making the defect inspection tool, such as an optical system, hard to detect the anomalies present on the wafer. It is due to the resolution of the conventional light sources used is no longer smaller than the dimension of anomalies. For advancing resolution in defect inspection, a more applicable inspection tool, such as an e-beam inspection tool, is introduced to semiconductor manufacturing processes inspection. Further, in VC (voltage contrast) mode inspection, the e-beam inspection tool can even discover under-layer defect, which is almost impossible for nowadays optical inspection systems. Hence, the e-beam inspection tool becomes more important in semiconductor processes.
In a regular anomaly hunting process, large field of view and VC mode inspection, a larger beam current (Ib) such as several hundreds nano-amperes (nA) are applied in the e-beam inspection systems. Once the anomalies are located, on the other hand, to review and analyze the cause of these anomalies requires high resolution of the e-beam inspection system and a smaller beam current such as several tens of pico-amperes (pA) are applied instead.
Up to the present, the only e-beam system can handle both larger currents and small currents inspection is disclosed by Wang et al. in “Charged Particle Beam Detection Unit with Multi Type Detection Subunits”, U.S. patent application Ser. No. 12/715,766 filed on Mar. 2, 2010. The previous multi type design is able to handle the large and small beam currents for both high resolution and high speed requirements. However, it sacrifices the side view function for stereo image.
The present invention provides a detection unit and a system that could perform regular a large range of beam current inspection with stereo image; perform defect review that requires high resolution and small beam current and perform defect review and fine defect inspection with stereo image.